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This is a handy, easy to build general purpose 50 watt amp. The amp has an input for a radio, TV, stereo or other line level device. It also has a phono input for a record player, guitar, microphone or other un-amplified source. With the addition of a low pass filter at the input, it makes a great amp for a small subwoofer.
| R1 | 1 | 200 Ohm 1/4 W Resistor | |
| R2 | 1 | 200K 1/4 W Resistor | |
| R3 | 1 | 30K 1/4 W Resistor | |
| R5 | 1 | 1K 1/4 W Resistor | |
| R6 | 1 | 5K 1/4 W Resistor | |
| R7,R10 | 2 | 1 Meg (5%) 1/2 W Resistor | |
| R8,R9 | 2 | 0.4 Ohm 5 W Resistor | |
| R11 | 1 | 10K Pot | |
| R12,R13 | 2 | 51K 1/4 W Resistor | |
| R14 | 1 | 47K 1/4 W Resistor | |
| C1 | 1 | 100uF 35V Electrolytic Capacitor | |
| C2 | 1 | 0.011uF Capacitor | |
| C3 | 1 | 3750pF Capacitor | |
| C4,C6 | 2 | 1000pF Capacitor | |
| C5,C7,C8 | 3 | 0.001uF Capacitor | |
| C9 | 1 | 50pF Capacitor | |
| C10 | 1 | 0.3uF Capacitor | |
| C11,C12 | 2 | 10,000uF 50V Electrolytic Capacitor | |
| U1,U2 | 2 | 741 Op Amp | |
| U3 | 1 | ICL8063 Audio Amp Transister Driver thingy | |
| Q1 | 1 | 2N3055 NPN Power Transistor | |
| Q2 | 1 | 2N3791 PNP Power Transistor | |
| BR1 | 1 | 250 V 6 Amp Bridge Rectifier | |
| T1 | 1 | 50V Center Tapped 5 Amp Transformer | |
| S1 | 1 | SPST 3 Amp Switch | |
| S2 | 1 | DPDT Switch | |
| F1 | 1 | 2 Amp Fuse | |
| SPKR1 | 1 | 8 Ohm 50W Speaker | |
| MISC | 1 | Case, Knobs, Line Cord, Binding Posts Or Phono Plugs (For Input And Output), Heatsinks For Q1 And Q2 |
1. I know I skipped R4. That is not a problem :-)
2. Distortion is less than 0.1% up to 100HZ and increases to about 1% at 20kHz.
3. I haven't been able to find anyone who sells a suitable T1. You can always use two 24V 5A units in series. If you are building two amps (for stereo), then I would suggest using an old microwave transformer and rewinding it. Follow the instructions in the 12V To 120V Inverter, execpt wind 26 turns, twist a loop (center tap) and wind 26 more turns. That should work out to around 50 volts. You may need to add or remove turns depending on your transformer.
4. Q1 and Q2 will require heatsinks.
5. You may have trouble finding U3 because it is discontinued. Please don't email me about sources...I can't find it either. See if any of the sources in Where To Get Parts has it. A possible source was sent in by JBWilliams:
Zigma Electronics 8803 Shirless Ave. Northbridge, CA 91324 United States Phone: 818-772-7590